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# Percentage nightmare

Topic Labels: Formulas
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Did you mean:  5 - Automation Enthusiast

Hello good people of airtable!

I would like to know how to:

add two percentages together, then minus that percentage from an amount? to get the sum of that calculation

in this case-

FEE (£40) - (CUT (10%) + TAX (20%) = 30%) = PROFIT (£28) 1 Solution

Accepted Solutions  18 - Pluto

Welcome to the Airtable community!

Try converting {CUT} to a rollup field, then use this formula

``````{FEE} * (1 - ({CUT} + {TAX}))
``````

When converting the lookup field to a rollup field, you can use the `SUM(values)` formula. Since there is only one value, the “sum” will the the same as the original value.

In general, I recommend using rollup fields instead of lookup fields in formulas whenever possible. Lookup fields have some weird behaviors in formula fields.

2 Replies 2  18 - Pluto

Welcome to the Airtable community!

Try converting {CUT} to a rollup field, then use this formula

``````{FEE} * (1 - ({CUT} + {TAX}))
``````

When converting the lookup field to a rollup field, you can use the `SUM(values)` formula. Since there is only one value, the “sum” will the the same as the original value.

In general, I recommend using rollup fields instead of lookup fields in formulas whenever possible. Lookup fields have some weird behaviors in formula fields.  5 - Automation Enthusiast

Thank you Kuovonne! very much appreciated :raised_hands:t2: 